Bacterial Abundance and Dehydrogenase Activity in Selected Agricultural Soils from Lublin Region

The aim of our study was to analyze the impact of soil agriculture management on bacterial abundance (expressed as total microorganism count plus copiotrophic and oligotrophic bacteria numbers) and soil dehydrogenase activity. Four different soil units agriculturally exploited (under oat-type crops) and the same number of control soils not agriculturally used were taken for study in April 2014 from the surface layer (0-20 cm). Under laboratory conditions the soils were subjected to analysis of: pH, total carbon, total microbial counts, copiotrophic and oligotrophic bacteria numbers, and dehydrogenase activity. The first consequences of agricultural practices were a decrease of pH toward acidic conditions and impoverishment of total carbon. Secondly, it was demonstrated that agricultural soil usage in relation to control sites affected biological properties by decreasing total microbial counts (by 20-75%), copio-and oligotrophic bacteria abundance (by 15-33%), and dehydrogenase activity (by 25-71). The ratio of oligotrophic to copiotrophic bacteria (O:C), being an indicator of soil biological balance, ranged 0.81-1.53 and 1.02-2.40 for arable and control soils, respectively. Lower values of biological factors observed in agricultural soils clearly indicated a progressive reduction of bacterial abundances and metabolic activities.